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   1 /* ir-rc5-decoder.c - handle RC-5 IR Pulse/Space protocol
   2  *
   3  * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation version 2 of the License.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  */
  14
  15 /*
  16  * This code only handles 14 bits RC-5 protocols. There are other variants
  17  * that use a different number of bits. This is currently unsupported
  18  * It considers a carrier of 36 kHz, with a total of 14 bits, where
  19  * the first two bits are start bits, and a third one is a filing bit
  20  */
  21
  22 #include <media/ir-core.h>
  23
  24 #define RC5_NBITS               14
  25 #define RC5_UNIT                888888 /* ns */
  26
  27 /* Used to register rc5_decoder clients */
  28 static LIST_HEAD(decoder_list);
  29 static DEFINE_SPINLOCK(decoder_lock);
  30
  31 enum rc5_state {
  32         STATE_INACTIVE,
  33         STATE_BIT_START,
  34         STATE_BIT_END,
  35         STATE_FINISHED,
  36 };
  37
  38 struct decoder_data {
  39         struct list_head        list;
  40         struct ir_input_dev     *ir_dev;
  41         int                     enabled:1;
  42
  43         /* State machine control */
  44         enum rc5_state          state;
  45         u32                     rc5_bits;
  46         int                     last_unit;
  47         unsigned                count;
  48 };
  49
  50
  51 /**
  52  * get_decoder_data()   - gets decoder data
  53  * @input_dev:  input device
  54  *
  55  * Returns the struct decoder_data that corresponds to a device
  56  */
  57
  58 static struct decoder_data *get_decoder_data(struct  ir_input_dev *ir_dev)
  59 {
  60         struct decoder_data *data = NULL;
  61
  62         spin_lock(&decoder_lock);
  63         list_for_each_entry(data, &decoder_list, list) {
  64                 if (data->ir_dev == ir_dev)
  65                         break;
  66         }
  67         spin_unlock(&decoder_lock);
  68         return data;
  69 }
  70
  71 static ssize_t store_enabled(struct device *d,
  72                              struct device_attribute *mattr,
  73                              const char *buf,
  74                              size_t len)
  75 {
  76         unsigned long value;
  77         struct ir_input_dev *ir_dev = dev_get_drvdata(d);
  78         struct decoder_data *data = get_decoder_data(ir_dev);
  79
  80         if (!data)
  81                 return -EINVAL;
  82
  83         if (strict_strtoul(buf, 10, &value) || value > 1)
  84                 return -EINVAL;
  85
  86         data->enabled = value;
  87
  88         return len;
  89 }
  90
  91 static ssize_t show_enabled(struct device *d,
  92                              struct device_attribute *mattr, char *buf)
  93 {
  94         struct ir_input_dev *ir_dev = dev_get_drvdata(d);
  95         struct decoder_data *data = get_decoder_data(ir_dev);
  96
  97         if (!data)
  98                 return -EINVAL;
  99
 100         if (data->enabled)
 101                 return sprintf(buf, "1\n");
 102         else
 103         return sprintf(buf, "0\n");
 104 }
 105
 106 static DEVICE_ATTR(enabled, S_IRUGO | S_IWUSR, show_enabled, store_enabled);
 107
 108 static struct attribute *decoder_attributes[] = {
 109         &dev_attr_enabled.attr,
 110         NULL
 111 };
 112
 113 static struct attribute_group decoder_attribute_group = {
 114         .name   = "rc5_decoder",
 115         .attrs  = decoder_attributes,
 116 };
 117
 118 /**
 119  * ir_rc5_decode() - Decode one RC-5 pulse or space
 120  * @input_dev:  the struct input_dev descriptor of the device
 121  * @duration:   duration of pulse/space in ns
 122  *
 123  * This function returns -EINVAL if the pulse violates the state machine
 124  */
 125 static int ir_rc5_decode(struct input_dev *input_dev, s64 duration)
 126 {
 127         struct decoder_data *data;
 128         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 129         u8 command, system, toggle;
 130         u32 scancode;
 131         int u;
 132
 133         data = get_decoder_data(ir_dev);
 134         if (!data)
 135                 return -EINVAL;
 136
 137         if (!data->enabled)
 138                 return 0;
 139
 140         if (IS_RESET(duration)) {
 141                 data->state = STATE_INACTIVE;
 142                 return 0;
 143         }
 144
 145         u = TO_UNITS(duration, RC5_UNIT);
 146         if (DURATION(u) == 0)
 147                 goto out;
 148
 149 again:
 150         IR_dprintk(2, "RC5 decode started at state %i (%i units, %ius)\n",
 151                    data->state, u, TO_US(duration));
 152
 153         if (DURATION(u) == 0 && data->state != STATE_FINISHED)
 154                 return 0;
 155
 156         switch (data->state) {
 157
 158         case STATE_INACTIVE:
 159                 if (IS_PULSE(u)) {
 160                         data->state = STATE_BIT_START;
 161                         data->count = 1;
 162                         DECREASE_DURATION(u, 1);
 163                         goto again;
 164                 }
 165                 break;
 166
 167         case STATE_BIT_START:
 168                 if (DURATION(u) == 1) {
 169                         data->rc5_bits <<= 1;
 170                         if (IS_SPACE(u))
 171                                 data->rc5_bits |= 1;
 172                         data->count++;
 173                         data->last_unit = u;
 174
 175                         /*
 176                          * If the last bit is zero, a space will merge
 177                          * with the silence after the command.
 178                          */
 179                         if (IS_PULSE(u) && data->count == RC5_NBITS) {
 180                                 data->state = STATE_FINISHED;
 181                                 goto again;
 182                         }
 183
 184                         data->state = STATE_BIT_END;
 185                         return 0;
 186                 }
 187                 break;
 188
 189         case STATE_BIT_END:
 190                 if (IS_TRANSITION(u, data->last_unit)) {
 191                         if (data->count == RC5_NBITS)
 192                                 data->state = STATE_FINISHED;
 193                         else
 194                                 data->state = STATE_BIT_START;
 195
 196                         DECREASE_DURATION(u, 1);
 197                         goto again;
 198                 }
 199                 break;
 200
 201         case STATE_FINISHED:
 202                 command  = (data->rc5_bits & 0x0003F) >> 0;
 203                 system   = (data->rc5_bits & 0x007C0) >> 6;
 204                 toggle   = (data->rc5_bits & 0x00800) ? 1 : 0;
 205                 command += (data->rc5_bits & 0x01000) ? 0 : 0x40;
 206                 scancode = system << 8 | command;
 207
 208                 IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
 209                            scancode, toggle);
 210                 ir_keydown(input_dev, scancode, toggle);
 211                 data->state = STATE_INACTIVE;
 212                 return 0;
 213         }
 214
 215 out:
 216         IR_dprintk(1, "RC5 decode failed at state %i (%i units, %ius)\n",
 217                    data->state, u, TO_US(duration));
 218         data->state = STATE_INACTIVE;
 219         return -EINVAL;
 220 }
 221
 222 static int ir_rc5_register(struct input_dev *input_dev)
 223 {
 224         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 225         struct decoder_data *data;
 226         int rc;
 227
 228         rc = sysfs_create_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 229         if (rc < 0)
 230                 return rc;
 231
 232         data = kzalloc(sizeof(*data), GFP_KERNEL);
 233         if (!data) {
 234                 sysfs_remove_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 235                 return -ENOMEM;
 236         }
 237
 238         data->ir_dev = ir_dev;
 239         data->enabled = 1;
 240
 241         spin_lock(&decoder_lock);
 242         list_add_tail(&data->list, &decoder_list);
 243         spin_unlock(&decoder_lock);
 244
 245         return 0;
 246 }
 247
 248 static int ir_rc5_unregister(struct input_dev *input_dev)
 249 {
 250         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 251         static struct decoder_data *data;
 252
 253         data = get_decoder_data(ir_dev);
 254         if (!data)
 255                 return 0;
 256
 257         sysfs_remove_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 258
 259         spin_lock(&decoder_lock);
 260         list_del(&data->list);
 261         spin_unlock(&decoder_lock);
 262
 263         return 0;
 264 }
 265
 266 static struct ir_raw_handler rc5_handler = {
 267         .decode         = ir_rc5_decode,
 268         .raw_register   = ir_rc5_register,
 269         .raw_unregister = ir_rc5_unregister,
 270 };
 271
 272 static int __init ir_rc5_decode_init(void)
 273 {
 274         ir_raw_handler_register(&rc5_handler);
 275
 276         printk(KERN_INFO "IR RC-5 protocol handler initialized\n");
 277         return 0;
 278 }
 279
 280 static void __exit ir_rc5_decode_exit(void)
 281 {
 282         ir_raw_handler_unregister(&rc5_handler);
 283 }
 284
 285 module_init(ir_rc5_decode_init);
 286 module_exit(ir_rc5_decode_exit);
 287
 288 MODULE_LICENSE("GPL");
 289 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 290 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 291 MODULE_DESCRIPTION("RC-5 IR protocol decoder");